Sunrise 5:24 AM   Sunset 10:27 PM Moonrise 3:57 AM   Moonset 10:53 PM

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FXAK68 PAFC 081320 AFDAFC

Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 520 AM AKDT Wed May 8 2024

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)...

Multiple shortwave troughs are moving north around a large upper low sitting out over the Bering Sea this morning, one now crossing the Alaska range, and the other nearing the Gulf Coast this morning. A surface low southeast of Middleton Island is expected to lift north with the new shortwave lifting towards Southcentral, eventually moving into Prince William Sound this afternoon as it weakens and shears apart over high terrain.

Looking at the pattern into the remainder of the week, things will unfortunately look much more reminiscent of fall than late spring. As the shortwave trough and low arriving near the Gulf Coast begin to move inland this afternoon, rain and higher elevation snow will spread from the coastline into interior Southcentral, first into the Kenai Peninsula, then up into Anchorage and the Mat-Su Valleys. Lighter rainfall is expected to briefly lift past lower elevations of the Copper River Basin, with amounts of generally a tenth of an inch or less through tonight not expected to noticeably exacerbate ongoing flooding concerns across the Glennallen area. Farther east, heavier rainfall amounts as high as half an inch will be possible with the main wave of precipitation moving through Anchorage and the Mat-Su through tonight.

Late tonight into Thursday morning, steady rain will end from south to north as the shortwave trough exits towards the northern Alaska Range. Rapid pressure rises at the surface behind the trough passage will also lead to a short lived burst of stronger gap winds late tonight into early Thursday, most notably out of the Copper River up into Gulkana/Glennallen. Gusty gap winds will also be aided by a push of cold air advection from the south until the pressure gradient weakens along the coast later on Thursday morning. Cooler than average temperatures will prevail as cooler air streams in from the Gulf, with widely scattered rain showers and mountain snow showers expected to persist in general.

The main low in the Bering will swing east into Kodiak Island and the western Gulf by Thursday afternoon, pushing another wave of showers past Kodiak before becoming yet another open wave trough on approach to Southcentral. There is some lingering uncertainty regarding the exact trajectory with the main energy with this trough, but overall expect more cold rain to spread back into the Prince William Sound and out to the Mat-Su/Anchorage areas as the wave lifts north late Thursday night into Friday morning. Low level temperatures will start out notably cooler than what we'll have in place for this evening's rainfall event. While accumulating snow is not likely down to sea level, we very well could see falling snow reach all the way down to the lowest elevations for a short time late Thursday night into Friday across the Mat-Su and Anchorage before the trough axis lifts to the north on Friday. Cooler than normal but drier conditions (except near Kodiak) will persist into Friday.

-AS

.SHORT TERM FORECAST SOUTHWEST ALASKA, THE SEA AND THE ALEUTIANS (Days 1 through 3)...

A broad upper low resides over the central Bering Wednesday morning with weak high pressure over Southwest Alaska and the Western Aleutians. Low pressure over the Gulf of Alaska has aided in the movement of easterly wave activity along the boundary into interior Bristol Bay, and forecast models suggest this precipitation may continue into the afternoon.

A polar low near the Pribilof Islands drops southward across the Alaska Peninsula. The low will bring cooler temperatures, gusty winds, and snow. The combination of winds and snow will result in periods of reduced visibility down to one half mile. Gusty conditions are expected to linger into Wednesday evening from Nikolski to Unalaska. Westerly gusts up to 45 mph will be possible.

After the polar low departs the Aleutians and moves into the North Pacific, a Kamchatka Low is forecast to spread a broad front into the Aleutians through Thursday night. Widespread precipitation will accompany the front and span the Aleutian Chain as it tracks from west to east, beginning Wednesday night.
Previously cooler temperatures over the Aleutians should lift northward and become replaced by warmer North Pacific temperatures. Thus, any initial snow will be brief and quickly transition to rain.



.LONG TERM FORECAST (Days 4 through 7: Saturday through Tuesday)...

A broad upper level trough extends across the Bering and most of Mainland Alaska through the forecast period. A weak upper ridge moves out of the Russian Far East Sunday, but flattens out over the Aleutians by Tuesday. Model guidance is good through late Sunday, but becomes uncertain across the Aleutians as the ridge collapses and a new overall flow sets up. A couple new features out of Siberia begin to influence the pattern Tuesday. A well developed upper low moves across the Alaska Peninsula into the Gulf of Alaska by Sunday, then weakens and opens to a broad trough for Tuesday. Its surface reflection moves from the Eastern Aleutians into the Gulf, spreading a very active weather pattern along its track Eastward.

Widespread precipitation spread across the Aleutians, AKPEN and Southwest Alaska into Kodiak Island Saturday, and continues along the Eastern Kenai Peninsula into Prince William Sound and the rest of Southcentral Alaska through Sunday before tapering off in the Western portions. Locally heavy rainfall is expected for coastal locations from the Eastern Aleutians and AKPEN, over Kodiak Island, and across to the Gulf into Monday, with decreasing amounts moving inland. Gusty surface winds to just below gale force levels precede the low across the Gulf through Sunday before diminishing. Breezy conditions over the Eastern Bering and Bristol linger into Monday.

- Kutz

AVIATION

PANC... VFR ceilings this morning likely to begin transitioning to MVFR by this afternoon. Variable winds this morning will shift southerly similarly by the afternoon, introducing gusts up to 20 mph through this evening. Showers are expected to develop over the terminal by this afternoon as well with reductions in visibility possible down to MVFR levels. Showers to become increasingly sparse by late this evening.

Kvichak
Click for Map
Wed -- 12:15 AM AKDT     -1.01 feet Low Tide
Wed -- 04:46 AM AKDT     18.01 feet High Tide
Wed -- 05:57 AM AKDT     Moonrise
Wed -- 06:11 AM AKDT     Sunrise
Wed -- 01:09 PM AKDT     1.82 feet Low Tide
Wed -- 04:17 PM AKDT     14.05 feet High Tide
Wed -- 10:38 PM AKDT     Sunset
Tide / Current data from XTide NOT FOR NAVIGATION

Kvichak, Kvichak River, Alaska, Tide feet

Kvichak Bay (off Naknek River entrance)
Click for Map
Wed -- 12:27 AM AKDT     3.42 knots Max Flood
Wed -- 04:00 AM AKDT     -0.00 knots Slack
Wed -- 06:00 AM AKDT     Moonrise
Wed -- 06:14 AM AKDT     Sunrise
Wed -- 07:10 AM AKDT     -2.51 knots Max Ebb
Wed -- 10:53 AM AKDT     0.01 knots Slack
Wed -- 12:44 PM AKDT     2.07 knots Max Flood
Wed -- 03:28 PM AKDT     -0.01 knots Slack
Wed -- 06:58 PM AKDT     -3.10 knots Max Ebb
Wed -- 10:38 PM AKDT     Sunset
Wed -- 10:50 PM AKDT     0.00 knots Slack
Tide / Current data from XTide NOT FOR NAVIGATION

Kvichak Bay (off Naknek River entrance), Alaska Current, knots

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